An IPS-LCD refers to an LCD in which liquid crystals are initially aligned in a horizontal direction with respect to a glass substrate and at a certain angle with respect to an electrode, and an electric field is formed in parallel to the glass substrate.
FIG. 1 illustrates a basic structure of a conventional IPS-LCD.
As illustrated in FIG. 1, the IPS-LCD includes a first polarizer 1, a second polarizer 2, and a liquid crystal panel 3. An absorption axis 4 of the first polarizer 1 and an absorption axis 5 of the second polarizer 2 are disposed perpendicular to each other. Also, the absorption axis 4 of the first polarizer and an optical axis 6 of a liquid crystal cell are disposed in parallel to each other.
Meanwhile, the liquid crystal panel 3 is manufactured by horizontally aligning liquid crystals 7 between two substrates, and an optical axis of the liquid crystal within the liquid crystal cell is in parallel to the polarizer.
Such IPS-LCD is categorized into an IPS-LCD, a super IPS-LCD, and a fringe field switching-LCD (FFS-LCD) according to an active matrix drive electrode mode including an electrode pair. The present invention is applied to all of the types of IPS-LCDs.
Since liquid crystals within the IPS-LCD are horizontally aligned, refractive index anisotropy according to viewing angle does not greatly change. Thus, the IPS-LCD is advantageous in that the difference in refractive index anisotropy between liquid crystals is small and a viewing angle is wide, as compared with a Twisted Nematic (TN) mode in which liquid crystals are vertically aligned. However, when viewed from the side, the alignment of the liquid crystals is asymmetric. Hence, color variation occurs at both a left side and a right side, and light leakage is relatively large with respect to a tilt angle. Consequently, a contrast ratio is lowered at a tilt angle.